End all services that have to do with Plesk, especially the ODBC and MySql modules. Then try again.
If it won't work, use the Microsoft Installation Clean-Up utility (
http://download.microsoft.com/download/e/9/d/e9d80355-7ab4-45b8-80e8-983a48d5e1bd/msicuu2.exe) to remove installation information regarding MySql and ODBC modules. Then try again.
If it works, use CCleaner (
www.ccleaner.com) to clean up the registry from Plesk related entries.